F1000Research 2021, 10:445 Last updated: 09 SEP 2021 RESEARCH ARTICLE Association between pesticide exposure and obesity: A cross- sectional study of 20,295 farmers in Thailand [version 1; peer review: awaiting peer review] Kajohnsak Noppakun1,2, Chudchawal Juntarawijit 3 1Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand 2Pharmacoepidemiology and Statistics Research Center (PESRC), Faculty of Pharmacy, Chiang Mai University, Chiang Mai, Thailand 3Faculty of Agriculture, Natural Resources and Environment, Naresuan University, Phitsanulok, 65000, Thailand v1 First published: 04 Jun 2021, 10:445 Open Peer Review https://doi.org/10.12688/f1000research.53261.1 Latest published: 04 Jun 2021, 10:445 https://doi.org/10.12688/f1000research.53261.1 Reviewer Status AWAITING PEER REVIEW Any reports and responses or comments on the Abstract article can be found at the end of the article. Background: Obesity is a serious condition because it is associated with other chronic diseases which affect the quality of life. In addition to diet and exercise, recent research has found that pesticide exposure might be another important risk factor. Methods: The objective of this large cross-sectional study was to determine the association between pesticide exposure and obesity among farmers in Nakhon Sawan and Phitsanulok province, Thailand. Data on pesticide use and obesity prevalence from 20,295 farmers aged 20 years and older was collected using an in-person interview questionnaire. The association was analysed using multivariable logistic regression, adjusted for its potential confounding factors. Results: Obesity was found to be associated with pesticide use in the past. The risk of obesity was significantly predicted by types of pesticides, including insecticides (OR = 2.27, 95% CI 1.09-4.74), herbicides (OR = 4.72, 95% CI 1.16-19.29), fungicides (OR = 2.17, 95% CI 1.37-3.44), rodenticides (OR = 2.52, 95% CI 1.59-3.99), and molluscicides (OR = 3.37, 95% CI 2.13-5.31). Among 35 surveyed individual pesticides, 24 were significantly associated with higher obesity prevalence (OR = 1.75, 95% CI 1.00-3.06 to OR = 8.37, 95% CI 3.97-17.64), including herbicide butachlor, 17 insecticides (three carbamate insecticides, five organochlorine insecticides, and nine organophosphate insecticides), and six fungicides. Conclusion: This study found obesity in farmers in Nakhon Sawan and Phitsanulok province, Thailand, to be associated with the long- term use of several types of pesticides. The issue should receive more public attention, and pesticide use should be strictly controlled. Keywords Pesticide exposure, obesity, farmer health, insecticide exposure, herbicide exposure, fungicide exposure Page 1 of 13 F1000Research 2021, 10:445 Last updated: 09 SEP 2021 Corresponding author: Chudchawal Juntarawijit ([email protected]) Author roles: Noppakun K: Conceptualization, Formal Analysis, Investigation, Methodology, Writing – Original Draft Preparation, Writing – Review & Editing; Juntarawijit C: Conceptualization, Data Curation, Funding Acquisition, Investigation, Methodology, Project Administration, Resources, Supervision, Validation, Writing – Original Draft Preparation, Writing – Review & Editing Competing interests: No competing interests were disclosed. Grant information: This project received grant support from the Thailand Science Research and Innovation (SRI) The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Copyright: © 2021 Noppakun K and Juntarawijit C. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. How to cite this article: Noppakun K and Juntarawijit C. Association between pesticide exposure and obesity: A cross-sectional study of 20,295 farmers in Thailand [version 1; peer review: awaiting peer review] F1000Research 2021, 10:445 https://doi.org/10.12688/f1000research.53261.1 First published: 04 Jun 2021, 10:445 https://doi.org/10.12688/f1000research.53261.1 Page 2 of 13 F1000Research 2021, 10:445 Last updated: 09 SEP 2021 Abbreviations BMI: body mass index CM: carbamate pesticide CVD: cardiovascular diseases 2,5-DCP: 2,5-dichlorophenol DDT: dichlorodiphenyltrichloroethane EDC: endocrine-disrupting chemicals ICD-10: International Classification of Diseases 10th OC: organochlorine pesticide OPs: organophosphate pesticide PCBs: polychlorinated biphenyl p,p'-DDE: dichlorodiphenyldichloroethylene VHV: village health volunteers Background Obesity is a global public health problem. In 2016, the World Health Organization (WHO) reported that there were approximately two billion people aged 18 years and older who were overweight, of which 650 million were obese, with this number expected to rise.1 In Thailand, the latest national survey reported obesity prevalence among adults aged 18 years and older, to be 4.0% class I obesity (body mass index (BMI) 30.0-34.9 kg/m2), 0.8% class II obesity (BMI 35.0-39.9 kg/m2), and 0.1% class III obesity (BMI ≥40.0 kg/m2).2 Obesity is not just an image problem, it can also affect health and well-being. Obesity has been linked with various health problems, including cardiovascular disease (CVD), type 2 diabetes mellitus (T2DM), cancer, and other health problems including liver and kidney disease, sleep apnea, and depression, which can eventually lead to mortality.3 Many factors can affect obesity, including age, genes, diet, a sedentary lifestyle, certain diseases, and medications, as well as other health conditions including sleeping habits, stress, and depression.4 Recent studies have found that pesticide exposure may be associated with metabolic disorders such as obesity.5 Mice studies have reported that chlorpyrifos, an organophosphate pesticide, has interfered with mucus-bacterial interactions in the gut, leading to increased lipopolysaccharide entry into the body resulting in excess fat storage.6 A study in Korea found women with Methanobacteriales, a bacteria in the gut that is linked to obesity, have higher body weight and waist circumference.7 This finding was consistent with a study in the United States of America (U.S.A) that with the use of the National Health and Nutrition Examination Survey (NHANES), found that obesity in adults was associated with the fumigant insecticide paradichlorobenzene,8 and 2,5-dichlorophenol (2,5-DCP) exposure.9 In a cohort study, dichlor- odiphenyldichloroethylene (p,p'-DDE), and polychlorinated biphenyl (PCBs) were associated with higher BMI, high triglyceride levels, and insulin resistance.10 A recent study also linked a simultaneous exposure to bisphenol A (BPA), bisphenol S (BPS), and mono (carboxyoctyl) phthalate (MCOP), to an elevated risk of obesity.11 As far as we know, to date, this issue has not been investigated in Thailand. This cross-sectional study aimed to determine the association between pesticide exposure and obesity among farmers in Nakhon Sawan and Phitsanulok province, Thailand. Identification of individual pesticides to predict the risk of obesity was the main interest. The results will be useful for verification of previous results and prevention of obesity. Methods Study design and setting Data in this cross-sectional study was collected from farmers in Nakhon Sawan and Phitsanulok province, Thailand. Nakhon Sawan province is located about 250 km north of Bangkok, Thailand, with a population of 1,066,455 people and 401,432 households, from 15 districts (data for the year 2016). The majority of people are farmers, and the main crops are rice, sugarcane, and cassava. In 2017, the province had a gross domestic product (GDP) of 21,852 THB (716 USD).12 In 2019, Phitsanulok province, located 377 km north of Bangkok, had a population of 865,368 people from nine districts and 342,787 households. Agriculture is the biggest sector of the economy, generating about 28% of GDP with an employment rate of 41.9%. The major crops in the province are rice, sugar cane, cassava, and vegetables13 (Thailand Information Centre, n.d.). Study participants and sampling procedure Study participants were farmers aged 20 years and older, who had worked as farmers for at least five years. Participants were selected using multistage sampling. Firstly, three districts from each province were randomly selected. In each district, three sub-districts were further randomly selected. In each sub-district, we selected 2,100-4,500 farmer families, accounting for about 30-100% of all farmer families in each sub-district. Using data from the local authority and personal contact, village health volunteers (VHV) identified farmer families, who were contacted for data collection. In each family, one adult who met the inclusion criteria was interviewed. Page 3 of 13 F1000Research 2021, 10:445 Last updated: 09 SEP 2021 All local hospitals inside the selected subdistrict were contacted and public health staff and its membership VHV were invited to participate in the study. VHV who had mobile phone and internet access to the online questionnaires were recruited. These volunteers also had to attend a one-day training session to be informed about the project and to be trained on interviewing the participants, along with the correct use of online questionnaires. Most of the interviews took place in the participant’s home, however sometimes in other places, e.g. local temple or hospital. Data was collected